N-alkylated derivatives of [D-Pro10]dynorphin A-(1-11) are high affinity partial agonists at the cloned rat kappa-opioid receptor.
As part of an effort to develop peptides with selective kappa-opioid antagonist activity, a series of N-alkylated [D-Pro10]dynorphin A-(1-11) derivatives were made through solid-phase peptide synthesis: R-Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-D-Pro-LysOH, where R = N-benzyl, N-cyclopropylmethyl, N,N-dicyclopropylmethyl, or N,N-diallyl. These derivatives and dynorphin A-(1-13)NH2 were evaluated for kappa-opioid receptor binding affinity and potency as inhibitors of adenylyl cyclase. Equilibrium competition binding experiments using [3H]diprenorphine (approximately 600 pM) were performed on membranes prepared from cultured Chinese hamster ovary (CHO) cells stably expressing the rat kappa-opioid receptor. Tissue prepared from this cell line was used to evaluate opioid peptide inhibition of forskolin-stimulated (50 microM) adenylyl cyclase activity. Displacement of [3H]diprenorphine specific binding by these peptides was observed with a rank order of affinity (Ki, nM) = [D-Pro10]dynorphin A-(1-11) (0.13) > dynorphin A-(1-13)NH2 (0.34) > N-cyclopropylmethyl- (1.4) > N,N-dicyclopropylmethyl- (12.6) approximately N-benzyl- (18.3) approximately N,N-diallyl-[D-Pro10]dynorphin A-(1-11) (26.0). A similar rank order was observed for potency of adenylyl cyclase inhibition (IC50, nM): [D-Pro10]dynorphin A-(1-11) (0.12) approximately dynorphin A-(1-13)NH2 (0.19) > N-cyclopropylmethyl- (2.7) > N,N-dicyclopropylmethyl- (13.2) approximately N,N-diallyl- (18.0) approximately N-benzyl-[D-Pro10]dynorphin A-(1-11) (36.4). The peptides differed in their percent maximal inhibition of adenylyl cyclase activity: dynorphin A-(1-13)NH2 (100%) approximately N-cyclopropylmethyl- (94.3%) approximately [D-Pro10]dynorphin A-(1-11) (87.9%) > N-benzyl- (71.4%) >> N,N-dicyclopropylmethyl- (23.6%) approximately N,N-diallyl-[D-Pro10]dynorphin A-(1-11)(18.9%). As the N,N-dicyclopropylmethyl- and N,N-diallyl-[D-Pro10]dynorphin A-(1-11) derivatives were found to have only weak partial agonist activity with respect to adenylyl cyclase inhibition, they were evaluated for their ability to reverse dynorphin A-(1-13)NH2 (10 nM) inhibition of adenylyl cyclase activity. N,N-dicyclopropylmethyl- and N,N-diallyl-[D-Pro10]dynorphin A-(1-11) reversed dynorphin A-(1-13)NH2 inhibition to levels equal to the maximal inhibition produced by N,N-dicyclopropylmethyl- and N,N-diallyl-[D-Pro10]dynorphin A-(1-11) alone. This weak partial agonism combined with nanomolar potency render the N,N-dicyclopropylmethyl- and N,N-diallyl-[D-Pro10]dynorphin A-(1-11) compounds promising leads for further attempts to synthesize peptide kappa-opioid receptor antagonists.
Soderstrom
K
K
College of Pharmacy, Oregon State University, Corvallis 97331, USA.
Choi
H
H
Berman
F W
FW
Aldrich
J V
JV
Murray
T F
TF
D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000478:Alkylation; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D004174:Diprenorphine / Q000378:metabolism; D004399:Dynorphins / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D017473:Receptors, Opioid, kappa / Q000819:agonists* / Q000235:genetics
D000067956:Adenylyl Cyclase Inhibitors; D004791:Enzyme Inhibitors; D009292:Narcotic Antagonists; D010446:Peptide Fragments; D017473:Receptors, Opioid, kappa; D004174:Diprenorphine; D004399:Dynorphins; C044619:dynorphin (1-11), Pro(10)-; D000262:Adenylyl Cyclases